First, it is nice to meet another adult student!
Second, I think as adults we have very high expectations of ourselves. I'm proficient in my profession, and I find it very frustrating and demoralizing not to be proficient at the piano. However, I think, based upon my experience, that starting an instrument at middle age presents more challenges than starting as a child. I know I have ingrained habits of body and mind which I struggle with...my fingers aren't as flexible as they were when I was a kid, my mind tends to wander over my to do list when I should be working on a piece.
What has helped me is to preplan every practice session with the intent of working on specific tasks supporting goals. Right now I'm working on a Chopin Prelude, a Mozart Sonata and a Schubert Impromtu. At the close of each lesson, I ask my teacher what I should be working on during the forthcoming week and that is my priority A list. I then play those sections of each piece first in my lesson, get an assignment regarding them or moving forward for the next week.
I think it is hard to feel you are making progress without some "map". Perhaps asking your teacher to help design one each week would give you a feeling of forward motion.